1. Field of the Invention
The invention generally relates to detachment procedures, and more particularly, to handling detachment procedures for only non-emergency services upon expiration of a Closed Subscriber Group (CSG) subscription while resources for emergency services also exist.
2. Description of the Related Art
In a typical mobile communication environment, a user equipment (UE) may communicate voice and/or data signals with one or more service networks via cellular stations of the service networks. The wireless communications between the UE and the service networks may be in compliance with various wireless technologies, such as the Global System for Mobile communications (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, Code Division Multiple Access 2000 (CDMA 2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, and others.
Take the WCDMA or LTE technology in compliance with the 3GPP TS 24.008 specification, v.9.1.0 (referred to herein as the TS 24.008 specification) and the 3GPP TS 24.301 specification, v.9.1.0 (referred to herein as the TS 24.301 specification) for example. After a UE is powered on and connects to a WCDMA or LIE system, it will need to perform an attachment procedure to register itself to the WCDMA or L′I′E system so that it can obtain mobile communication services from the WCDMA or LTE system. As shown in FIG. 1, the attachment procedure starts by the UE transmitting an ATTACH REQUEST message to the WCDMA or LTE system (step S110). When receiving the ATTACH REQUEST message, the WCDMA or LTE system authenticates the UE, checks if the UE is authorized to have access to mobile communication services, and performs a security mode control procedure to activate the encryption on the subsequent messages in the connection (step S120). If none of the checks fail, the WCDMA or LTE system accepts the attachment request by transmitting an ATTACH ACCEPT message to the UE (step S130). Specifically, the ATTACH ACCEPT message includes configuration information for activating the resources for the mobile communication services. In response to the ATTACH ACCEPT message, the UE establishes the resources for the mobile communication services according to the configuration information (step S140), and transmits an ATTACH COMPLETE message to the WCDMA or LTE system (step S150), to acknowledge that it has received the ATTACH ACCEPT message. If the ATTACH COMPLETE message is received successfully, the attachment procedure ends and the mobile communication services may be provided to the UE.
Later, a detachment procedure may be initiated to de-register the UE from the WCDMA or LIE system. The UE may initiate the detachment procedure for reasons, such as the switching off of the UE, the removal of the Universal Subscriber Identity Module (US') card, or disablement of the wireless module of the UE. Alternatively, the UE may be handed over to another WCDMA or UE system where the UE does not have access to the packet data service, and the WCDMA or LTE system may initiate the detachment procedure. FIG. 2 is a message sequence chart illustrating a detachment procedure initiated by a UE. The UE first transmits a DETACH REQUEST message to the WCDMA or LIE system to de-register itself from the WCDMA or LIE system for mobile communication services (step S210). When receiving the DETACH REQUEST message, the WCDMA or LIE system locally deactivates all established resources for the mobile communication services (step S220). Subsequently, the WCDMA or LTE system transmits a DETACH ACCEPT message to the UE to inform that the detachment request has been accepted (step S230). After receiving the DETACH ACCEPT message, the UE accordingly deactivates the established resources for the mobile communication services, and the detachment procedure ends (step S240).